In an apparatus that produces or inspects microscopic patterns such as circuit patterns of magnetic heads and semiconductor devices, circuit patterns of masks, reticles or the like for forming circuit patterns of semiconductor devices and so forth, a charged-particle beam is irradiated to these targets (sample) to produce or inspect the circuit patterns.
Hereinafter, described as an example is an electron beam rendering apparatus which renders a circuit pattern on a sample using an electron ray (electron beam). The electron beam rendering apparatus causes generation of an electron ray in an ultra-high vacuum environment to scan a semiconductor substrate with the electron ray, and forms an LSI pattern on a substrate such as a glass substrate to manufacture masks or reticles used in an exposure apparatus such as a stepper.
FIG. 6 is a view showing a construction of a conventional electron beam rendering apparatus. Referring to FIG. 6, an electron ray outputted from a column 1 (projection system) is irradiated to a sample 10 placed on a stage 4 of a sample chamber 3. The position of the sample 10 is controlled by measuring the position of a mirror 20 fixed to a stage 4 using a laser beam. Since a laser beam in the air is easily influenced by fluctuation of the air and variation of the air pressure, an interferometer 21 is provided in a vacuum. It is preferable to measure the position of the sample 10 with the column 1 as a reference. Therefore, the interferometer 21 is arranged on the lower surface of the upper partition 3A of the sample chamber 3 where the relative position of the sample 10 with respect to the column 1 is easily adjusted.
The sample chamber 3 is mounted on the base 8, which is supported by mounting 5 having a function of vibration isolation. A main table 7 holding the mounting 5 is placed on a base 6 which is placed on a floor 9. The column 1, which is arranged on the upper partition 3A of the sample chamber 3 with high rigidity, is exhausted to a vacuum by a column exhaustion vacuum pump 50, so that the internal atmosphere of the column 1 is maintained in a high vacuum (e.g., equal to or lower than 10−4 Pa). The sample chamber 3 is exhausted to a vacuum by a sample chamber vacuum pump 40 so that the internal atmosphere of the sample chamber 3 is maintained in a high vacuum (e.g., on the order of 10−4 Pa).
The conveyance path of the sample 10 is described. The sample 10 is conveyed from an outside, which is an air atmosphere, to a preliminary exhaustion chamber 30 adjacent to the sample chamber 3 by a conveyer 31 provided inside the preliminary exhaustion chamber 30. Then, the preliminary exhaustion chamber 30 is preliminarily exhausted from an air state to a vacuum state by a vacuum pump (not shown). When the preliminary exhaustion chamber 30 has about the same degree of vacuum as that of the sample chamber 3, a valve 32 is opened to convey the sample 10 to the stage 4. The sample 10 is then subjected to circuit pattern rendering or transferring (exposure), conveyed from the sample chamber 3 to the preliminary exhaustion chamber 30, and conveyed to the outside after the preliminary exhaustion chamber 30 returns from the vacuum state to the air atmosphere. The foregoing series of operation enables conveyance of the sample 10 while keeping the sample chamber 3 in a vacuum state, and helps improve the throughput.
The column exhaustion vacuum pump 50 is connected to the column 1 through a column exhaustion bellows 50A, and held by a table 51 supported by the base 8. In the foregoing conventional art, the mounting arrangement method can be found in Japanese Patent Application Laid-Open (KOKAI) No. 05-074695, and the method of setting the sample chamber and the column can be found in Japanese Patent Application Laid-Open (KOKAI) No. 08-320570.
In an electron beam exposure apparatus, in order to prevent an energy loss of an electron ray, the path of the electron ray must be maintained in a high vacuum as mentioned above. However, in the conventional apparatus structure, a large measurement error of the sample position is about to become a problem.
Recently samples (exposure target), particularly wafers, tend to have a large bore diameter to improve productivity, and the number of chip acquisition per wafer is increasing. For this reason, it has become necessary to increase the stroke of the stage 4 for moving the sample 10, and naturally the sample chamber 3 has been enlarged. Therefore, the rigidity of the sample chamber 3 becomes vulnerable to vibration disturbance from the floor 9 or the vacuum pump 40. Because of the above-described reason, the following error factors are reinforced in the conventional apparatus structure.
When the vibration disturbance from the floor 9 or the vacuum pump 40 causes elastic vibration in the sample chamber 3, the attitude of the column 1 mounted to the sample chamber 3 as well as the positions of the interferometer 21 and optical member 23 fluctuate, causing an error. FIG. 7 shows fluctuation of the position of the laser optical member 23 due to elastic vibration of the sample chamber 3. FIG. 8 shows elastic deformation of the upper partition 3A and a slant of the column 1 caused by elastic vibration of the sample chamber 3. Due to these fluctuation, deformation, slant and so forth, the following errors occur.
(1) Electron Beam Shift Due to Displacement ΔY of the Column 1
If the column 1 is displaced by ΔY, the irradiated electron beam shifts. Therefore, it is necessary to add the electron beam shift ΔY to the position information of the sample 10, which is measured with the column 1 as a reference.
(2) Length Measurement Error Due to Displacement ΔX of the Interferometer 21
If the interferometer 21 is displaced by ΔX, an error ΔX is added to the position information of the sample 10, which is measured with the column 1 as a reference.
(3) Abbe Error Due to Displacement ΔZ of the Interferometer 21
When the interferometer 21 is displaced by ΔZ, if the stage 4 undergoes pitching θp, the following length measurement error is generated:ΔZ·sin θp
(4) Cosine Error Due to Rotation Δθ of the Interferometer 21
If the interferometer 21 rotates by Δθ, the following length measurement error is generated:L(1−cos Δθ); L: measurement length
As a method of reducing the above-described various errors, it may be considered to increase the rigidity of the partitions that constitute the sample chamber 3. However, in this case, an increased load to the mounting 5 due to an increased mass of the sample chamber 3 is inevitable.
Furthermore, it is possible to reduce the above-described errors (1) and (2) by employing a structure in which a reference beam of the interferometer is irradiated to a reference mirror 25 mounted to the column 1. However, in this case, optical axis adjustment becomes complicated, resulting in an increased operation time.